This document claims priority rights of and is based on Japanese patent application Nos. JPAP10-304263 filed on Oct. 26, 1998 and JPAP11-150207 filed on May 28, 1999 in the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to a method and apparatus for optical disk recording, and more particularly to a method and apparatus for optical disk recording which is capable of efficiently performing an optimum laser power calibration on a recordable optical disk including a CD-R (compact disk recordable), and a CD-RW (compact disk re-writable).
2. Description of the Related Art
Reading and writing techniques for compact disks (CD) used as optical mass-storage mediums for computers have greatly been improved in recent years. As a result, many types of compact disks have been developed. These types includes CD-ROM (compact disk read only memory), CD-R (compact disk recordable), and CD-RW (compact disk re-writable). While CD-ROM is a read only memory type compact disk, CD-R and CD-RW are recordable. The CD-R is a one-time data recordable type that allows users to write once so as to manufacture salable disks. The CD-RW is a re-writable type that allows writing, reading, and erasing multiple times.
In general, the laser power required for an optical disk recording is variable and is dependant upon various characteristics of an optical disk, such as the magnetic recording medium, the laser diode employed in the recording drive unit, etc. An optimum laser power calibration is a common technique to prevent such a problem. Typically, the optimum laser power calibration includes performing a test recording before executing an actual data recording by applying laser power with a stepwise change in a power calibration area (PCA) which is normally allocated in the innermost track of an optical disk. In addition, many optical recording apparatus perform the optimum laser power calibration by controlling the optical disk to rotate at a constant linear velocity (CLV) during recording so as to satisfy a data recording format for the constant linear velocity, which is a widely used data recording format for a CD (compact disk) recording. However, this CLV data recording requires an accurate control of a spindle motor in order to achieve the constant linear velocity. When the spindle motor rotates at a higher velocity, the control must be more accurate and the time to stabilize the rotation is increased.
In recent years, there has been a clear trend for a faster transmission than the standard transmission rate with respect not only to playback of an optical disk but also to recording. For this reason, an optical disk recording apparatus is expected to use a constant angular velocity (CAV) for the CLV formatted disks as well as for the CAV formatted disks.
However, the CAV recording is problematic in that the optimum recording condition varies with the linear velocity. This problem becomes more apparent with higher linear velocity. In particular, a relatively great gap of the linear velocity may be generated between the PCA allocated at the innermost track and the data area in which an actual data recording is performed.
There have been provided several optical disk recording apparatus which increase laser power in order to record data at a rotation velocity higher than a standard rotation velocity and which have been thought as to be able to solve the above-described problem. Japanese Laid-Open Patent Publication No. 06-176364 (1994) is one example of these apparatus. However, these apparatus cannot ensure a successful high-speed data recording relative to an optical disk rotating at a constant angular velocity.
Accordingly, an object of the present invention is to provide a novel optical disk recording apparatus that is capable of efficiently performing an optimum laser power calibration.
Another object of the present invention is to provide a novel method for efficiently performing an optimum laser power calibration on a recordable optical disk.
To achieve these and other objects, a novel optical disk recording apparatus includes a memory, a laser recording unit, a first motor, a second motor, an asymmetry information detect mechanism, and a controller. The memory stores data including values of an initial recording laser power and a reference asymmetry of a playback signal. The laser recording unit emits laser light, where the amount of laser light emission is determined according to a value of a recording laser power supplied, and records data, using the laser light emitted, on a recording surface of a recordable optical disk having a data recording area and a test recording area thereon. The first motor rotates the recordable optical disk. The second motor moves the laser recording unit in and out along a radius of the recording surface of the recordable optical disk. The asymmetry information detect mechanism detects asymmetry information of a playback signal from data recorded in the recordable optical disk. The controller performs an optimum laser power calibration relative to a specific area in the data recording area when required to record data in a specific area. During the optimum laser power calibration, the controller instructs the laser recording unit to move to a test location in the test recording area and the first motor to rotate the recordable optical disk at a linear velocity which is the same as the linear velocity at which the data recording is to be performed at the specific area and performs the test recording at the test location for a predetermined number of times using the initial recording laser power stored in the memory with a stepwise change each time. Further, the controller reads asymmetry values of playback signals detected by the asymmetry detect mechanism from data recorded by the test recording, selects an optimum asymmetry value closest to the reference asymmetry, and determines an optimum recording laser power according to the selected optimum asymmetry.
In one preferred embodiment, the controller performs the optimum laser power calibration when there is a relatively small difference of inner radius between locations of starting and ending of data recording in the data recording area.
The controller may divide the specific area into a plurality of data fields and the test recording area into a same plurality of test fields, perform the optimum laser power calibration relative to each of the plurality of data fields using each of the same plurality of test fields, and may store to the memory the optimum recording laser power determined for each of the plurality of data fields through the optimum laser power calibration.
In another preferred embodiment, the controller performs the optimum laser power calibration when there is a relatively great difference of inner radius between locations of starting and ending of data recording in the data recording area.
The controller may divide the data recording area into a plurality of data fields and the test recording area into a same plurality of test fields, perform the optimum laser power calibration relative to each of at lease one of the plurality of data fields where data is recorded using at least one of the same plurality of test fields, and may store to the memory the optimum recording laser power determined for each of the at least one of the plurality of data fields through the optimum laser power calibration.
Further, the above-mentioned optical disk recording apparatus may include a laser light detect mechanism for detecting an amount of the laser light which is emitted by the laser recording unit during the test recording. Then, the amount of the laser light detected by the laser light detect mechanism may be stored in the memory together with the optimum recording laser power determined according to the selected optimum asymmetry.
The controller may record the optimum recording laser power determined through the optimum laser power calibration in each of the plurality of data fields.
The controller may increase the frequency of a laser pulse for generating the laser power in proportion to an increase of the linear velocity during the data recording and the test recording.
Further, to achieve the above-mentioned objects, a novel method for performing an optimum laser power calibration on an optical disk includes the steps of storing, providing, and executing. The storing step stores values of an initial recording laser power and a reference asymmetry of a playback signal. The providing step provides laser recording means, which is movable in and out along a radius of the recording surface of the recordable optical disk, for emitting laser light, where the amount of laser light is determined according to a value of a recording laser power supplied, and recording data, using the laser light emitted, on a recordable surface of a recordable optical disk having a data recording area and a test recording area on a recording surface thereof The executing step executes an optimum laser power calibration relative to a specific area in the data recording area when required to record data in the specific area. The optimum laser power calibration includes the steps of instructing, rotating, performing, detecting, reading, selecting, and determining. The instructing step instructs the laser recording means to move to a test location in the test recording area. The rotating step rotates the recordable optical disk at a linear velocity which is the same as a linear velocity at which the data recording is to be performed at the specific location. The performing step performs a test recording at the test location for a predetermined number of times using the initial recording laser power with a stepwise change each time. The detecting step detects asymmetry information of a playback signal from data recorded in the recordable optical disk during the test recording. The reading step reads asymmetry values of the playback signals generated through the test recording for the predetermined number of times. The selecting step selects an optimum asymmetry value closest to the reference asymmetry. The determining step determines an optimum recording laser power according to the selected optimum asymmetry.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.